by OTHA W. LINTON N THE DAYS following his discovery of new, invisible ray in November 1895 Professor wilhelm Conrad roentgen experimented doggedly to test its properties He noted quickly that solid objects placed in the beam between the Crookes’ tube and the fluorescent screen serving a a receptor attenuated or blocked the beam depending upon their density and structure BEAM LINE 25
BEAM LINE 25 I N THE DAYS following his discovery of a new, invisible ray in November, 1895, Professor Wilhelm Conrad Roentgen experimented doggedly to test its properties. He noted quickly that solid objects placed in the beam between the Crookes’ tube and the fluorescent screen serving as an image receptor attenuated or blocked the beam, depending upon their density and structure. Medical Applications of X Rays by OTHA W. LINTON
A CENTURY OF RADIOLOGY: 1895-1995 The discovery of the X ray in 1895 was one of the most momentous events in science and medicine, but it was only the beginning of what was to be accomplished in the nexi 00 years in radiology. What follows are some highlights provided by American College of Radiology. 1895 German physics professor Wilhelm Cora Then, in a heart-stopping moment, he chanced to ers the x ray on November 8 in his laboratory in Wurzburg On December 28, Roentgen announces his discovery with a ass his hand through the beam. as he looked at the scientific paper, W. C Roentgen: About A New Kind of Rays screen, the flesh of the hand seemingly melted away, (preliminary communication), that is widely reprinted projecting only the outlines of the bones. The hand was intact, unharmed. But on the screen, only the bones 1896 showed up. With that observation, the science of On January 23, Roentgen delivers his first lecture about the medical radiology was born. X Roentgens discovery launches a flurry of experimentation A few days later, Roentgen made a photographic image around the world with the Crookes tubes. Researchers study of his wife's hand, using the new rays instead of light for what the X rays will do and tinker with refining the design of the exposure. Again, only the bones showed, this time the tubes. Although the shapes and configurations of the on a permanent record which others could see-and be- tubes change, the basic concept will stay the same until lieve 1913. The discovery of a new form of energy that could Fluoroscopy is invented in January by Italian scientist Enrico penetrate solid objects and record their structure excited Salvioni, while American inventor Thomas Edison, an early Roentgen,s scientific contemporaries. But it was the and active X-ray enthusiast, works on a similar device. The fluoroscope is a hand-held or mounted device consisting of skeletal hand that captured the imagination of the public an oblong box, one end of which fits tightly against the eyes, and of physicians, who recognized instantly that this the opposite end of which is a fluorescent screen. The basic discovery could change medical practice forever. concept is still used today. A century later, the vastly more sophisticated In March, a"Roentgen photograph is introduced as evidence medical imaging are still based upon the recog in a Montreal courtroom by a man suing a defendant who that body parts absorb a beam of X rays according to allegedly shot him. The X ray proves the presence of a bullet density, producing an image which allows identification not detected by exploratory surgery. of body structures as well as the recognition of abnor- malities reflective of injury and disease conditions. people with and without medical qualifications One of the first physicians to specialize in X rays in 1896 is Take a chest X-ray image, for example. The calcium Dr Francis Henry Williams of Boston. He is also a graduate density of the spine and ribs blocks the most X rays, of the Massachusetts Institute of Technology, making him one leaving white areas on a film. No X rays penetrate to of the few physicians intimately conversant with the physics expose the film and darken those spots. The water that create X rays. He is instrumental in early uses of X rays densities of the stomach and liver are grayish. They block for medical diagnosis, including the use of fluoroscopy to less of the X-ray beam than bones. It's easy to see the study the blood vessels. Later this will be known as contrast between them. The fat density of muscles is angiography. less than that of the water. They look only slightly dark- 1898 er, but the distinction is there for a trained eye. Final In December, Marie and Pierre Curie, working in Paris ly, the air spaces in the lungs allow penetration of most discover radium. a new element that emits 200 million times of the X-ray beam, and look almost black on the films. more radiation than uranium. In 1903. the Curies and Allow that the chest X-ray image looks complex Antoine-Henni Becquerel share the Nobel Prize in Physics because three dimensions are recorded as two muscle for their work on radioactivity. tissue overlies the ribs, which in turn overlie the lung Like the discovery of X rays, the discovery of radium cap- tured the world's imagination, says Nancy Knight, Ph. D, his- cavities. The shapes of blood vessels(water density) and torian and director of the Center for the American History of the esophagus, which carries food and liquids to the Radiology. "Scientists knew that the radiation from X rays and stomach. can be seen fractures of the ribs abnormal radium was similar, but radium was considered the natural curves of the spine, unusual heart silhouettes are readily version of X rays visible. Irregular shadows, caused by cancers growing in the lung, may require a sophisticated viewer to pick 26 SUMMER 1995
26 SUMMER 1995 A CENTURY OF RADIOLOGY: 1895–1995 The discovery of the X ray in 1895 was one of the most momentous events in science and medicine, but it was only the beginning of what was to be accomplished in the next 100 years in radiology. What follows are some highlights provided by American College of Radiology. 1895 • German physics professor Wilhelm Conrad Roentgen discovers the X ray on November 8 in his laboratory in Würzburg. • On December 28, Roentgen announces his discovery with a scientific paper, W. C. Roentgen: About A New Kind of Rays (preliminary communication), that is widely reprinted. 1896 • On January 23, Roentgen delivers his first lecture about the X rays. • Roentgen’s discovery launches a flurry of experimentation around the world with the Crookes’ tubes. Researchers study what the X rays will do and tinker with refining the design of the tubes. Although the shapes and configurations of the tubes change, the basic concept will stay the same until 1913. • Fluoroscopy is invented in January by Italian scientist Enrico Salvioni, while American inventor Thomas Edison, an early and active X-ray enthusiast, works on a similar device. The fluoroscope is a hand-held or mounted device consisting of an oblong box, one end of which fits tightly against the eyes, the opposite end of which is a fluorescent screen. The basic concept is still used today. • In March, a “Roentgen photograph” is introduced as evidence in a Montreal courtroom by a man suing a defendant who allegedly shot him. The X ray proves the presence of a bullet not detected by exploratory surgery. • Hospitals begin acquiring X-ray equipment to be used by people with and without medical qualifications. • One of the first physicians to specialize in X rays in 1896 is Dr. Francis Henry Williams of Boston. He is also a graduate of the Massachusetts Institute of Technology, making him one of the few physicians intimately conversant with the physics that create X rays. He is instrumental in early uses of X rays for medical diagnosis, including the use of fluoroscopy to study the blood vessels. Later this will be known as angiography. 1898 • In December, Marie and Pierre Curie, working in Paris, discover radium, a new element that emits 200 million times more radiation than uranium. In 1903, the Curies and Antoine-Henri Becquerel share the Nobel Prize in Physics for their work on radioactivity. “Like the discovery of X rays, the discovery of radium captured the world’s imagination,” says Nancy Knight, Ph.D., historian and director of the Center for the American History of Radiology. “Scientists knew that the radiation from X rays and radium was similar, but radium was considered the ‘natural’ version of X rays.” Then, in a heart-stopping moment, he chanced to pass his hand through the beam. As he looked at the screen, the flesh of the hand seemingly melted away, projecting only the outlines of the bones. The hand was intact, unharmed. But on the screen, only the bones showed up. With that observation, the science of medical radiology was born. A few days later, Roentgen made a photographic image of his wife’s hand, using the new rays instead of light for the exposure. Again, only the bones showed, this time on a permanent record which others could see—and believe. The discovery of a new form of energy that could penetrate solid objects and record their structure excited Roentgen’s scientific contemporaries. But it was the skeletal hand that captured the imagination of the public and of physicians, who recognized instantly that this discovery could change medical practice forever. A century later, the vastly more sophisticated arts of medical imaging are still based upon the recognition that body parts absorb a beam of X rays according to their density, producing an image which allows identification of body structures as well as the recognition of abnormalities reflective of injury and disease conditions. Take a chest X-ray image, for example. The calcium density of the spine and ribs blocks the most X rays, leaving white areas on a film. No X rays penetrate to expose the film and darken those spots. The water densities of the stomach and liver are grayish. They block less of the X-ray beam than bones. It’s easy to see the contrast between them. The fat density of muscles is less than that of the water. They look only slightly darker, but the distinction is there for a trained eye. Finally, the air spaces in the lungs allow penetration of most of the X-ray beam, and look almost black on the films. Allow that the chest X-ray image looks complex because three dimensions are recorded as two. Muscle tissue overlies the ribs, which in turn overlie the lung cavities. The shapes of blood vessels (water density) and the esophagus, which carries food and liquids to the stomach, can be seen. Fractures of the ribs, abnormal curves of the spine, unusual heart silhouettes are readily visible. Irregular shadows, caused by cancers growing in the lung, may require a sophisticated viewer to pick
The famous radiograph made by Roentgen on December 22, 1895. This is traditionally known as"the first X-ray picture"and"the radiograph of Mrs Roentgens hand. However, it was not actually the first X-ray picture (others exposed photographic plates to X rays previously, without knowing the images' significance), and was not labeled as Mrs Roentgens hand when it was first published up in the welter of overlapping shad- kill more cancer cells while sparing ows. The pattern of coal particles normal ones are also parts of this etained in the lung field of miners century of remarkable progress may be even more subtle, but is es were essential to a diagnosis of black lung. more useful to surgeons than to other doctors. Bone fractures or displace- N THE WEEKS after the first ments, gallstones, kidney stones, and medical X-ray images early in bullets or other metallic fragments 1896, scientists and physicians could be located reliably With the 2 began to improve on the faint images improved tubes and films that a produced by tubes and generators like relaced the original glass plates the ones Roentgen used. How they doctors began to see organ shapes made improvements-borrowing But they still could not see into from advances in physics, chemistry, organs, which had the same water pharmacology, nuclear science, com- density inside and out. puters, telemetry and information Nevertheless, other advances science-is the story of a century of came quickly. In 1896, the Invento medical radiology Thomas edison devised the fluoro- Those early X-ray experiments scope, a calcium tungstate coated also led scientists to observe that the screen which glowed when X rays hit passage of X rays through living it, allowing direct viewing of any part tissue could cause changes. The low- of the anatomy. In 1913, William D energy Xrays appeared to have a good Coolidge of the General Electric effect on many skin diseases. Open Laboratories devised an improved hot cancers shrank and the sores dried cathode X-ray tube which produced up Arthritis sufferers reported relief consistent repeated exposures and from their pains. When exposures was shielded to prevent the scattered were seen to make hair fall out, the radiation that had harmed the early X ray was touted as an end to mens X-ray users. X-rays emerged from daily shaving chores. But just as Coolidge's tubes only through an This much admired" first radiograph quickly, workers with X rays noted aperture in the lead shielding. The of the human brain"from 1896is actually a pan of cat intestines that repeated exposures seemed to patient could then be placed into the Since the X ray was so novel to the cause skin inflammations, ulcers, beam while others were kept away public, falsified images appeared sores, superficial and deeper cancers, from it. Additionally, filters were frequently after Roentgens discovery. ood abnormalities, and even death. devised to absorb soft, useless X rays, The question arose: must X-ray and a device called a grid, placed in workers inevitably forfeit their own front of the film, absorbed much of health, as some pioneers did, to the the X-ray scatter that could cause promise of this new science? fuzzy images. Screens similar to the 8 The struggles of radiation scien- fluoroscope surface were used in film tists to develop radiation safety holders to enhance X-ray images protocols, to devise measurements, And the problem of looking to learn to control X-ray production, within body structures was finally g and to exploit the seeming para- addressed as well. Liquids opaque g dox that higher energies of radiation to X rays were found that could 5 BEAM LINE 27
BEAM LINE 27 up in the welter of overlapping shadows. The pattern of coal particles retained in the lung field of miners may be even more subtle, but is essential to a diagnosis of black lung. I N THE WEEKS after the first medical X-ray images early in 1896, scientists and physicians began to improve on the faint images produced by tubes and generators like the ones Roentgen used. How they made improvements—borrowing from advances in physics, chemistry, pharmacology, nuclear science, computers, telemetry and information science—is the story of a century of medical radiology. Those early X-ray experiments also led scientists to observe that the passage of X rays through living tissue could cause changes. The lowenergy X rays appeared to have a good effect on many skin diseases. Open cancers shrank and the sores dried up. Arthritis sufferers reported relief from their pains. When exposures were seen to make hair fall out, the X ray was touted as an end to men’s daily shaving chores. But just as quickly, workers with X rays noted that repeated exposures seemed to cause skin inflammations, ulcers, sores, superficial and deeper cancers, blood abnormalities, and even death. The question arose: must X-ray workers inevitably forfeit their own health, as some pioneers did, to the promise of this new science? The struggles of radiation scientists to develop radiation safety protocols, to devise measurements, to learn to control X-ray production, and to exploit the seeming paradox that higher energies of radiation The famous radiograph made by Roentgen on December 22, 1895. This is traditionally known as “the first X-ray picture” and “the radiograph of Mrs. Roentgen’s hand.” However, it was not actually the first X-ray picture (others exposed photographic plates to X rays previously, without knowing the images’ significance), and was not labeled as Mrs. Roentgen’s hand when it was first published. German Museum, Munich This much admired “first radiograph of the human brain” from 1896 is actually a pan of cat intestines. Since the X ray was so novel to the public, falsified images appeared frequently after Roentgen’s discovery. American College of Radiology kill more cancer cells while sparing normal ones are also parts of this century of remarkable progress. The earliest X-ray images were more useful to surgeons than to other doctors. Bone fractures or displacements, gallstones, kidney stones, and bullets or other metallic fragments could be located reliably. With the improved tubes and films that relaced the original glass plates, doctors began to see organ shapes. But they still could not see into organs, which had the same water density inside and out. Nevertheless, other advances came quickly. In 1896, the inventor Thomas Edison devised the fluoroscope, a calcium tungstate coated screen which glowed when X rays hit it, allowing direct viewing of any part of the anatomy. In 1913, William D. Coolidge of the General Electric Laboratories devised an improved hot cathode X-ray tube, which produced consistent repeated exposures and was shielded to prevent the scattered radiation that had harmed the early X-ray users. X-rays emerged from Coolidge’s tubes only through an aperture in the lead shielding. The patient could then be placed into the beam while others were kept away from it. Additionally, filters were devised to absorb soft, useless X rays, and a device called a grid, placed in front of the film, absorbed much of the X-ray scatter that could cause fuzzy images. Screens similar to the fluoroscope surface were used in film holders to enhance X-ray images. And the problem of looking within body structures was finally addressed as well. Liquids opaque to X rays were found that could
Around the world people believe radium to have marvelous medicinal properties. It is said to lessen constipation, lower blood pressure, cure insomnia by soothing the nerves, and increase sexual activity, and is put in skin creams and tooth- pastes. People flock to radium springs, where the water is mildly radioactive, a craze that lasts into the 1930s, and use radium drinkers c vessels made of irradiated earth. at radium cocktail parties, where inside everyone's drink is a vial of radium emanation-radon gas-to make the drinks glow be ingested or otherwise placed within a patient. For in the dark. Also popular is 'radium roulette, in which the instance. barium sulfate. a common mineral could roulette balls and table are painted with radioactive paint. be ground up and swallowed to outline the esophagus stomach and small intestine. barium sulfate could also German scientists friedrich Giesel and Friedrich Walkhoff be inserted as an enema to visualize the large intes- discover that radium rays are dangerous to the skin, Pierre tine. This practice allowed the viewing of strictures, Curie purposely leaves a radium sample on his arm for ten blockages, ulcers, cancers, and other defects. But the de- hours and produces a sunburn-like rash. En route to a confer velopment of other radio-opaque liquids, now called con- ence, Henri Becquerel unthinkingly carries a sample in his trast agents, which could be used with the kidney lower vest pocket and suffers a burn on his abdomen. the brain and spinal canal, the circulatory system and Radiology begins to emerge as a medical specialty. It lungs, took much longer and required far more becomes increasingly clear that producing an X-ray image requires skill and technical know-how, and interpreting the image requires a knowledge of anatomy OENTGEN'S DISCOVERY was artificial ionizing radiation. Two years later, a French physicist, Roentgen wins the first Nobel Laureate in Physics prize Henri Becquerel, discovered that certain rocks for his discovery emitted natural ionizing radiation with characteristics much like Roentgens X rays. Becquerel's colleagues 1904 Pierre and Marie Curie refined the naturally radioactive Clarence Dally, Thomas Edisons assistant in X-ray research, lies of extreme and repeated X-ray exposure. X rays had ores to derive uranium, polonium, and radium already caused severe burns on his face, hands, and arms Radium was perceived to have a value in treating resulting in several amputations. From this point on, the risks cancers, already seen to be responsive toXrays.Marie posed by radium and X rays become more clear. X-ray use Curie's work produced only tiny amounts, with one begins to be confined largely to doctors offices and hospitals. ounce of radium being offered for sale at S1 million.The radium salt(usually radium sulfate)was sealed in hol 1910 low gold or platinum needles and inserted into or against nd metal shields are commonly used to shield cancerous lumps to deliver cell-killing doses of radia- X tion. a decay product of radium, radon gas, was used 1917 in hollow glass seeds for insertion in tumors which could During World War I, X-ray equipment is an accepted compo- not be reached with the removable needles nent of aid stations and hospitals in the field William Coolidge soon improved his X-ray tubes to deliver energy levels of 200 kilovolts and more, and as 1919 doctors used radium coupled with the high energy X-ray Dr. Carlos Heuser, an Argentine radiologist, is the first to use beams, they noted the seeming paradox that higher a contrast medium in a living human circulatory system. The mpound, potassium iodide diluted with water, is acceptable energies killed more cancer cells and spared more normal because it is excreted by the body and causes the blood ves- tissue than lower-energy radiation. Radiobiologists came sels to appear opaque on the X-ray image. Dr Heuser suc- to understand that the rapid mitosis of cancer cells made cessfully injects the compound into a vein of a patient's hand them more susceptible to radiation destruction and less and simultaneously takes an X ray to visualize the veins in capable of regeneration than slower-growing normal the forearm and arm. His discovery, however, is lost on the cells. but because some normal cells were necessarily scientific world because it is published only in Spanish, in an radiated in the process of getting the energy to the Argentine medical joumal cancers, the success of treatment depended upon the ability of the radiologist to plan and deliver a dose that would kill all of the cancer cells without destroying an unacc nt of normal cells 28 SUMMER 1995
28 SUMMER 1995 be ingested or otherwise placed within a patient. For instance, barium sulfate, a common mineral, could be ground up and swallowed to outline the esophagus, stomach, and small intestine. Barium sulfate could also be inserted as an enema to visualize the large intestine. This practice allowed the viewing of strictures, blockages, ulcers, cancers, and other defects. But the development of other radio-opaque liquids, now called contrast agents, which could be used with the kidneys, the brain and spinal canal, the circulatory system and the lungs, took much longer and required far more complex solutions. ROENTGEN’S DISCOVERY was artificial ionizing radiation. Two years later, a French physicist, Henri Becquerel, discovered that certain rocks emitted natural ionizing radiation with characteristics much like Roentgen’s X rays. Becquerel’s colleagues Pierre and Marie Curie refined the naturally radioactive ores to derive uranium, polonium, and radium. Radium was perceived to have a value in treating cancers, already seen to be responsive to X rays. Marie Curie’s work produced only tiny amounts, with one ounce of radium being offered for sale at $1 million. The radium salt (usually radium sulfate) was sealed in hollow gold or platinum needles and inserted into or against cancerous lumps to deliver cell-killing doses of radiation. A decay product of radium, radon gas, was used in hollow glass seeds for insertion in tumors which could not be reached with the removable needles. William Coolidge soon improved his X-ray tubes to deliver energy levels of 200 kilovolts and more, and as doctors used radium coupled with the high energy X-ray beams, they noted the seeming paradox that higher energies killed more cancer cells and spared more normal tissue than lower-energy radiation. Radiobiologists came to understand that the rapid mitosis of cancer cells made them more susceptible to radiation destruction and less capable of regeneration than slower-growing normal cells. But because some normal cells were necessarily radiated in the process of getting the energy to the cancers, the success of treatment depended upon the ability of the radiologist to plan and deliver a dose that would kill all of the cancer cells without destroying an unacceptable amount of normal cells. Around the world people believe radium to have marvelous medicinal properties. It is said to lessen constipation, lower blood pressure, cure insomnia by soothing the nerves, and increase sexual activity, and is put in skin creams and toothpastes. People flock to radium springs, where the water is mildly radioactive, a craze that lasts into the 1930s, and use ‘radium drinkers,’ ceramic vessels made of irradiated earth, at radium cocktail parties, where inside everyone’s drink is a vial of ‘radium emanation’—radon gas—to make the drinks glow in the dark. Also popular is ‘radium roulette,’ in which the roulette balls and table are painted with radioactive paint. 1900 • German scientists Friedrich Giesel and Friedrich Walkhoff discover that radium rays are dangerous to the skin; Pierre Curie purposely leaves a radium sample on his arm for ten hours and produces a sunburn-like rash. En route to a conference, Henri Becquerel unthinkingly carries a sample in his lower vest pocket and suffers a burn on his abdomen. • Radiology begins to emerge as a medical specialty. It becomes increasingly clear that producing an X-ray image requires skill and technical know-how, and interpreting the image requires a knowledge of anatomy. 1901 • Roentgen wins the first Nobel Laureate in Physics prize for his discovery. 1904 • Clarence Dally, Thomas Edison’s assistant in X-ray research, dies of extreme and repeated X-ray exposure. X rays had already caused severe burns on his face, hands, and arms, resulting in several amputations. From this point on, the risks posed by radium and X rays become more clear. X-ray use begins to be confined largely to doctor’s offices and hospitals. 1910 • Eye goggles and metal shields are commonly used to shield X-ray users. 1917 • During World War I, X-ray equipment is an accepted component of aid stations and hospitals in the field. 1919 • Dr. Carlos Heuser, an Argentine radiologist, is the first to use a contrast medium in a living human circulatory system. The compound, potassium iodide diluted with water, is acceptable because it is excreted by the body and causes the blood vessels to appear opaque on the X-ray image. Dr. Heuser successfully injects the compound into a vein of a patient’s hand and simultaneously takes an X ray to visualize the veins in the forearm and arm. His discovery, however, is lost on the scientific world because it is published only in Spanish, in an Argentine medical journal
X-ray image of coins made by physicist A W. Goodspeed and photographer William Jennings in 1896, duplicating one they had made by accident realize its significance, and the photographic plates lay unnoticed and unremarked until Roentgens announcement of the X-ray discovery caused them to review the imag t the university of Cal- vals for treatment to take advantage ifornia in Berkeley. Lawrence invited of the mitotic cycle, ways of pro- Robert Stone, the chief of radiology tecting normal parts of the patient, at the University of California medical care to protect patients Medical Center in San Francisco, to e against infections, and other prod- bring cancer patients for treatment ucts of white blood-cell radiation with neutrons produced in the a destruction all began to contribute Donner lab Cancers treated with to improved radiation treatment. neutrons melted away. Soon, so did 3 Even so, surgery remained the first the cancer patients. Neutrons had 2 choice of treatment for many more energy and different biological of cancers, leaving radiation characteristics than high energy adjunctive method for destroying Xrays. Stone discontinued his treat cancer cells not removed by surgery ments until the characteristics of and for trying to control metastases neutrons could be understood better from advanced cancers World War Il arrived, and in quick succession Lawrence. Stone, and D URING THE FIRST four most of the leading radiation decades of this century, scientists in the free world were many advances in medical drawn into the Manhattan project radiation uses came from gradual to develop an atomic bomb. Wartime improvements in equipment and imperatives drive science more techniques. The availability of X-ray strongly than peaceful objectives. But machines in military hospitals dur- there was an appreciation within the ing World War I convinced many Manhattan project that biological physicians of the usefulness of X-ray problems were created by the phys- studies in detection of somatic prob- ical and chemical advances, and lems, as well as trauma. A chest after the war, the congress created X ray became the standard method the Atomic Energy Commission to of diagnosing tuberculosis. About all further peaceful applications of the that could be offered the active new radiation science tubercular patient was nursing care, but isolation of such patients helped OR PHYSICIANS. these peace. to break the spread of the highly ful applications took two contagious disease to other family directions. One was the devel members and co-workers. Tubercu- opment of artificial reactor-produced losis was the target of the first X-ray isotopes as high energy sources fo population screening efforts radiation treatment. During the The creation of artificial isotopes years, there had been development in the 1930s by Frederic Joliot and of Robert van de graaffs million volt Irene Curie, daughter of Pierre and static generators and Donald Kerst's Marie, opened new dimensions in high energy betatron, the first radiation science. Soon, Ernest supervoltage therapy machines. But Lawrence was making artificial iso- the simplicity of using cobalt 60 topes in the cyclotron of the Donner or cesium 137 in rotating- head BEAM LINE 29
BEAM LINE 29 X-ray image of coins made by physicist A.W. Goodspeed and photographer William Jennings in 1896, duplicating one they had made by accident in Philadelphia in 1890. When the two made the 1890 radiograph, they did not realize its significance, and the photographic plates lay unnoticed and unremarked until Roentgen’s announcement of the X-ray discovery caused them to review the images. American College of Radiology Optimal dose levels, time intervals for treatment to take advantage of the mitotic cycle, ways of protecting normal parts of the patient, medical care to protect patients against infections, and other products of white blood-cell radiation destruction all began to contribute to improved radiation treatment. Even so, surgery remained the first choice of treatment for many kinds of cancers, leaving radiation as an adjunctive method for destroying cancer cells not removed by surgery and for trying to control metastases from advanced cancers. DURING THE FIRST four decades of this century, many advances in medical radiation uses came from gradual improvements in equipment and techniques. The availability of X-ray machines in military hospitals during World War I convinced many physicians of the usefulness of X-ray studies in detection of somatic problems, as well as trauma. A chest X ray became the standard method of diagnosing tuberculosis. About all that could be offered the active tubercular patient was nursing care, but isolation of such patients helped to break the spread of the highly contagious disease to other family members and co-workers. Tuberculosis was the target of the first X-ray population screening efforts. The creation of artificial isotopes in the 1930s by Frédéric Joliot and Irene Curie, daughter of Pierre and Marie, opened new dimensions in radiation science. Soon, Ernest Lawrence was making artificial isotopes in the cyclotron of the Donner Laboratory at the University of California in Berkeley. Lawrence invited Robert Stone, the chief of radiology at the University of California Medical Center in San Francisco, to bring cancer patients for treatment with neutrons produced in the Donner lab. Cancers treated with neutrons melted away. Soon, so did the cancer patients. Neutrons had more energy and different biological characteristics than high energy X rays. Stone discontinued his treatments until the characteristics of neutrons could be understood better. World War II arrived, and in quick succession Lawrence, Stone, and most of the leading radiation scientists in the free world were drawn into the Manhattan project to develop an atomic bomb. Wartime imperatives drive science more strongly than peaceful objectives. But there was an appreciation within the Manhattan project that biological problems were created by the physical and chemical advances, and after the war, the congress created the Atomic Energy Commission to further peaceful applications of the new radiation science. FOR PHYSICIANS, these peaceful applications took two directions. One was the development of artificial reactor-produced isotopes as high energy sources for radiation treatment. During the war years, there had been development of Robert van de Graaff’s million volt static generators and Donald Kerst’s high energy betatron, the first supervoltage therapy machines. But the simplicity of using cobalt 60 or cesium 137 in rotating-head